A semiconductor device may function as a switching element that controls a current flowing between main electrodes by a voltage applied to a control electrode. An insulated gate bipolar transistor (hereinafter, referred to as IGBT), which is one kind of this semiconductor device having a trench insulated gate structure, can control a current flowing between a collector electrode and an emitter electrode by a voltage applied to a gate electrode. Since IGBT can control electric power ranging from dozens of watts to hundreds of thousands of watts and a wide switching frequency ranging from dozens of Hz to beyond hundreds of KHz, IGBT is widely used for power conversion systems from a small power application (for example, inverter, converter, chopper) to a large power application for railway, ironworks and the like.
IGBT is required to reduce the loss for increasing efficiency of the power conversion systems, that is, required to reduce the conduction loss and the switching loss. In addition, in order to avoid, for example, electromagnetic compatibility noises (hereinafter, referred to as EMC noises), malfunctions and breakdown of a motor, a capability of dV/dt control during the turn-off switching period by a control of a gate drive circuit is required depending on specifications of the application.
Then, Patent Document 1 of Japanese Patent Publication No. 2004-39838 proposes a method that improves a controllability of dV/dt by electrically connecting a floating p-layer to the emitter electrode through a resistance. In addition, Patent Document 2 of Japanese Patent Publication No. 2005-327806 proposes a structure that can reduce a switching loss by increasing the switching speed by increasing a ratio of gate-emitter capacity to gate-collector capacity by forming a trench instead of the floating p-layer of Patent Document 1 and filling the trench with an insulator film or a semiconductor layer.